Incorrect figures with Atan2 and Sqrt

• Question

• Hi,

I am having a problem woth Atan and Sqrt formulas. My Excel gives me a figure where my C# gives a different figure although it's the same formula.

The forumala in Excel is:

=2*ATAN2(SQRT(1-B15),SQRT(B15))

and in C#:

double the_c = Math.Atan2(Math.Sqrt(1 - the_a), Math.Sqrt(the_a));

Here is the Excelsheet:

https://www.jassimrahma.net/temp/DistanceAndBearingToWaypoint.zip

Here is my code and the problem is on the_c line

```current_latitude = 25.2680572;
current_longitude = 55.3159565;

double latt_from_radians = current_latitude * Math.PI / 180;
double long_from_radians = current_longitude * Math.PI / 180;
double latt_to_radians = HolyPlaceLatitude * Math.PI / 180;
double lang_to_radians = HolyPlaceLongitude * Math.PI / 180;

int the_r = 6371;            // for miles
// int r = 6371;            // for kilometers
// int r = 20, 903, 520;    // to get the result in feet

double law_of_cos_dist = Math.Acos((Math.Cos(latt_from_radians) * Math.Cos(latt_to_radians) * Math.Cos((-1 * lang_to_radians) - (-1 * long_from_radians))) + (Math.Sin(latt_from_radians) * Math.Sin(latt_to_radians))) * the_r;

LabelA.Text = law_of_cos_dist.ToString();

double the_a = Math.Pow((Math.Sin(dLat / 2)), 2) + Math.Cos(latt_from_radians) * Math.Cos(latt_to_radians) * Math.Pow((Math.Sin(dLong / 2)), 2);

LabelB.Text = the_a.ToString();

double the_c = Math.Atan2(Math.Sqrt(1 - the_a), Math.Sqrt(the_a));
LabelC.Text = the_c.ToString();
```

Kindly help...

Thanks,

Jassim

Sunday, August 18, 2019 12:39 AM